1. Field of the Invention
The present invention relates to an information signal transmission device such as video devices constituting an audio video system. More particularly, the present invention relates to the information signal transmission device that transmits and receives a message with no particular discrimination between outside and inside the device and with no particular discrimination between specified destinations and unspecified destinations, if viewed from an object within the device, by organizing information broadcasting means for broadcasting a message to a network and an event manager responsible for delivery of the message in a device, so that the network is released for the transmission of information signal as long as possible.
2. Description of the Related Art
In a conventional audio video (AV) system for transmitting information signal such as a video signal and audio signal, a video signal and an audio signal output by a tuner or a video cassette recorder are input to a television receiver through a dedicated analog line, and the television receiver is controlled through a remote control so that a desired video signal or a desired audio signal may be enjoyed.
If such an AV system is connected through a network to transfer video data and audio data, the interconnection of the video signal and audio signal is expected be simplified. A diversity of devices may be easily connected to the system as necessary. Through the network, various devices may be integrally managed to improve the ease of use of the AV system.
When the devices are integrally managed, the core device for controlling the entire operation of the system must monitor terminal devices. When an optical disk is changed on an optical disk player as a terminal device, for example, the core device of the system is required to detect the title of the optical disk newly loaded.
Among devices for receiving a television broadcast program, some receive satellite broadcast signals, some receive cable television signals, and the others receive ground waves, and in the system including such devices, the core device has to monitor receivable channels for all devices. There are times when new devices are added to the AV system increasing the receivable channels in the AV system.
To respond to the change in the state of each network terminal, the core device in the system regularly interrogates each device to detect a change with a sufficient time allowed. Such an interrogation shortens the time during which the network is released for the transfer of the video data and audio data, thereby leading to a failure to transmit the video data and audio data on a real-time basis.
The core device may place the same request with a group of devices as necessary, for example, may request all tuners connected to the network to report their channel lists. In such a case, the sender of such a request message has a difficulty detecting which ones of a plurality of devices are able to respond to the message. When a diversity of devices are simply connected to the network, this type of interrogation is thought of as a broadcasting with no particular destination specified. In succession to the broadcasting, there will be times when the connection configuration itself is changed.
In the one-to-one communication in which a destination of a message is specified, an acknowledgement is made, and a retransmission is requested in the event of a timeout to perform this type of interrogation. With this arrangement, however, the change of the lineup of the connected devices requires the sender to receive an acknowledgement from each of the destinations of a variable number for successful reception, making complex a communication procedure involved. When the connection happens to change between the acknowledgement from the destination and the communication of the message, a retransmission request is repeatedly made to a device that may have difficulty in responding to the interrogation. If a timeout is set in this case, a system error may be triggered. To assure the reliability of the system, the acknowledgement is essential and cannot be omitted.